The Pain Experience
Definition and Types of Pain:
- Pain Definition: Pain is described by the International Association for the Study of Pain (IASP) as an unpleasant sensory and emotional experience linked to actual or potential tissue damage.
- Acute Pain: Results from actual or threatened tissue damage and activates nociceptors.
- Chronic Pain: Persistent or recurrent pain lasting typically three months or more, including conditions like fibromyalgia, non-specific back pain, osteoarthritis, headaches, chronic cancer pain, and chronic post-surgical pain.
Biopsychosocial Model of Pain:
- The understanding of pain has evolved from a simple biomedical model to a comprehensive biopsychosocial approach, recognizing that pain is influenced by biomedical, psychological, and social factors. In chronic non-cancer pain (CNCP), social and psychological factors often dominate.
Individual Pain Experience:
- Pain and disability levels vary greatly among individuals with similar injuries.
- Responses to pain relief methods also vary individually.
- Communicating the pain experience can be challenging for patients, leading to frustration and distress.
Management of Pain:
- Effective pain management requires considering patients’ beliefs, needs, and expectations.
- Pain affects many aspects of a patient’s life, including daily activities, leisure, and sleep.
- Severe pain often correlates with a lower quality of life, with pain reduction being a primary goal for many patients.
- Building a collaborative partnership between patient and GP is crucial, emphasizing empathy and understanding.
Patient-Doctor Relationship:
- Patients need to feel their pain is understood and validated.
- It’s important to show interest in the patient as a person, not just their symptoms.
- Patients’ opinions on pain management should be valued.
- Optimism about improving their condition is essential.
Role of the GP:
- Patients may struggle with the involvement of multiple healthcare professionals, leading to confusion.
- Having a primary care doctor, ideally a GP, who knows the patient’s medical history and can coordinate care is important for effective management of chronic pain.
Placebo Effects:
- Placebo: A substance or procedure without inherent ability to produce an expected effect, but can have similar profiles to non-placebos.
- Placebo Response: Therapeutic response to a known placebo.
- Placebo Effect: Part of the therapeutic response not attributable to active ingredients, influenced by sociocultural treatment context.
Determinants of Placebo Effects:
- Influenced by doctor-patient relationship, expectancy, classical conditioning, and social/observational learning.
- Variability exists in degree and duration of placebo effects.
Pathways for Placebo Effects:
- Higher placebo analgesia when induced via suggestion combined with conditioning.
- Mediated by endogenous opioids, cholecystokinin, endogenous cannabinoid systems, and dopamine release.
Ethical Considerations and Practical Use:
- Placebos should not be administered deceptively.
- Using placebo effects to augment active treatments is becoming less contentious.
- More clinical research is needed to determine the practical value of placebos.
- Practitioners should consider how they deliver information to harness placebo effects and optimize treatment outcomes.
Pathophysiology-based Classification
Nociceptive Pain
- Definition: Arises from actual or threatened damage to non-neural tissue.
- Function: Guards against tissue injury and supports healing.
- Subtypes:
- Visceral Pain: Stimulation of nociceptors within the viscera.
- Somatic Pain: Stimulation of nociceptors in the musculoskeletal system.
- Duration: Typically lasts with continual noxious stimuli and resolves after tissue injury resolution.
- Chronic Nociceptive Pain: May occur in diseases like rheumatoid arthritis.
Neuropathic Pain
- Definition: Caused by a lesion or disease of the somatosensory nervous system.
- Causes: Mechanical trauma, metabolic diseases, neurotoxic chemicals, infection, tumor invasion.
- Diagnostic Criteria:
- Appropriate history.
- Signs of neurological deficit.
- Diagnostic interventions.
- Confirmation of underlying cause.
- Chronic Neuropathic Pain: Heterogeneous group of conditions.
- Co-occurrence: Nociceptive and neuropathic pain may coexist.
- Treatment: Less than ideal, with fewer than 50% achieving satisfactory relief.
Nociplastic Pain
- Definition: Pain from altered nociceptive processing without clear evidence of tissue damage or somatosensory system disease.
- Conditions: Fibromyalgia, complex regional pain syndrome (CRPS), non-specific chronic low back pain, functional visceral pain disorders.
- Mechanism: Altered function of nociceptive pathways.
Psychophysiological Approach
- Examined the influence of mental events on physical changes producing pain.
- General arousal models suggested prolonged ANS arousal and muscular contractions generate and perpetuate pain.
- Treatments like EMG, biofeedback, and relaxation techniques aim to reduce muscular tension and ANS arousal.
Current Theoretical Models
- Many acute musculoskeletal injuries do not resolve quickly, leading to chronic pain.
- Early intervention improves outcomes.
- The “Yellow Flags” concept screens for risk factors in developing chronic pain.
- Pincus et al. proposed an Integrated Biopsychosocial Risk-for-Disability Model, combining cognitive and behavioral factors.
Pain-Related Fear and Disability
- Acute pain associated with anxiety responses; chronic pain linked to vegetative signs of depressive disorders.
- Fear of pain can be more disabling than pain itself.
- Pain-related fear predicts performance and disability levels, with avoidance behaviors leading to physical deconditioning and chronicity.
- Chronic pain may result in physical deconditioning, lowering pain thresholds, and increasing the likelihood of avoiding activities.
Catastrophic Thinking and Pain-Related Fear
- Catastrophic thinking involves exaggerated orientation towards pain stimuli.
- Negative appraisals about pain can lead to persistent pain.
- Pain-related fear interferes with cognitive functions, leading to hyper-vigilance and difficulty shifting attention away from pain-related information.
Pain History Taking
General Assessment and Pain-Specific History
- Thorough History
- Chronic pain evaluation is crucial.
- Pain assessment as the “fifth vital sign.”
- Familiarity with the patient and input from families/support systems.
- Pain Characteristics
- Location
- Radiation
- Intensity
- Quality (sharp, dull, squeezing, throbbing, colicky)
- Temporal aspects (duration, onset, changes since onset)
- Constancy or intermittency
- Breakthrough pain characteristics
- Exacerbating/triggering factors
- Relieving factors
- Associated symptoms:
- Restricted range of motion, stiffness, swelling
- Muscle aches, cramps, spasms
- Color or temperature changes
- Changes in sweating, skin, hair, or nail growth
- Changes in muscle strength or sensation (dysesthesias/itching, numbness)
Psychosocial History Taking and Assessment
Pain Impact on Function and Quality of Life
- Social and Recreational Activities Interference with hobbies, socializing, travel
- Mood, Affect, and Anxiety Impact on energy, mood, personality
- Relationships Effect on family, friends, colleagues
- Occupation Impact on work responsibilities, hours, or cessation of work
- Sleep Interference with sleep
- Exercise Interference with exercise activities
- Activities of Daily Living (ADLs) and Instrumental Activities of Daily Living (IADLs)
- Bathing, dressing, toileting, feeding
- Shopping, using transportation, meal preparation, housework, managing finances and medications
Social Assessment
- Influences Family, work, life events, housing, sleep, activity, and nutrition
- Social Participation
- Participation in pleasurable activities (hobbies, movies, concerts, socializing, travel)
- Frequency of pain interference over the past week
- Mood and Relationships
- Pain’s impact on energy, mood, personality, and tearfulness
- Effect on relationships with family, significant others, friends, colleagues
- Occupational Impact
- Modification of work responsibilities and/or hours due to pain
- Time since last worked and reasons for stopping work
- Sleep and Exercise
- Pain interference with sleep and exercise
- Frequency of exercise and pain interference over the past week
- Isolation and Pain-Depression Cycle
- Social interactions, occupational performance, self-care
- Use of pain for sympathy, protection, benefits, or medico-legal compensation
Psychological Assessment
- Behavioral Assessment
- Explore patient’s personal and family history and support system
- Inquire about psychological disorders and substance abuse history
- Patient’s beliefs about pain and healthcare experiences
- Patient Perceptions
- Causes of persistent pain
- Adequacy of diagnostic work-up
- Expectations for specific treatments
- Goals for treatment (pain relief and functional improvement)
- Involvement in treatment planning and execution
- Mood State, Beliefs, Coping Skills
- Explore patient’s mood, beliefs, coping skills, behaviors, and responses contributing to pain experience
- Identify obstacles to recovery and treatment outcome
- Psychological Factors
- Use screening tools for mood and anxiety disorders
- Anxiety as a predictive factor for postoperative pain severity
- Association between chronic postsurgical pain (CPSP) and depression
- Relevant beliefs about diagnosis, prognosis, and treatment expectations
- Fear of pain contributing to avoidance responses and potential disability
- Negative, ruminative, and helpless thinking styles (e.g., catastrophic thinking)
Physical Examination
- Assessment for Signs of Tissue Damage/Injury or Disease
- Signs of nociceptive and/or neuropathic mechanisms of pain (e.g., tissue deformity, inflammation, neural disease or damage)
- Evaluation of Referred Pain Sources
- Including visceral sources
- Observations
- Hypervigilance or guarding with particular movements
- Compensatory postures and movements
- Evidence of allodynia, hypoalgesia, hyperalgesia
- Provisional Diagnosis
- Establish diagnosis for pain and biomedical mechanism involved
- Analyze disability level of the patient
Measurement of Pain and Functional Impact
- Pain Scoring Systems
- Verbal numerical rating scales for simplicity and consistency
- PEG scale for chronic musculoskeletal pain in general practice
- PEG scale scores (out of 30) as reference points for patient’s overall wellbeing
- Use of pain scores to compare patient assessments over time
Risk Assessment for Opioid Prescription
- Careful Prescription of Opioids: Opioids are effective analgesics but require careful prescribing to limit risks such as inappropriate use and diversion.
- High-Risk Groups for Problematic Opioid Usage:
- Younger Patients: Substance use issues generally commence before 35 years of age.
- Patients Without Definite Patho-Anatomic Diagnosis: Lack of clear diagnosis increases misuse risk.
- Patients with Active Substance Use Problems: Includes those in contact with individuals with substance use problems.
- Patients with Active Psychiatric Problems: Increases risk of misuse and side effects.
- Patients Using Benzodiazepines: Concomitant use substantially increases risks of cognitive impairment, sedation, and respiratory depression.
- Comprehensive Assessment:
- Address the risk of opioid misuse through thorough patient evaluation.
- Screening for opioid risk is recommended but lacks strong evidence of effectiveness.
- Treatment agreements and urine testing are recommended but have not significantly reduced opioid prescribing, misuse, or overdose rates.
- Patients with History of Substance Use Disorder (SUD):
- Higher risk of harm from opioids.
- Check state-based prescription monitoring systems.
- Generally, avoid offering opioids in general practice settings; refer to specialist services if pain control is unachievable by other means.
- Urine Drug Screening (UDS):
- May reveal substances unknown to the practitioner.
- Not all substances are routinely tested (e.g., specific request needed for oxycodone testing).
- If unexpected drugs (illicit or legal) are found, refer the patient for specialist assessment and management.
- Contact local pathology provider for necessary testing.